Study on decline and residue of spinosad in paddy using high performance liquid chromatography-tandem mass spectrometry

A residue analytical method of spinosad in paddy was established using high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) detection.The samples were extracted with acetonitrile,and purified on primary secondary amine(PSA) and graphitized carbon black(GCB),finally analyzed by HPLC-MS/MS.The method showed good linearity in the ranges of 0.006-1.2 mg/L,0.001-0.2 mg/L for spinosyns A and D with correlation coefficients(R2) of 0.990 5 and 0.994 9 respectively.The limits of detection(LOD) for spinosyns A and D were 0.001 mg/L in paddy water,and 0.005 mg/kg in paddy soil,rice plants,rice,rice husk and rice straw.The limits of quantification(LOQ) for spinosyns A and D in paddy water were 0.005 mg/L,and with 0.06 mg/kg,0.01 mg/kg respectively in rice matrices.The average recoveries of spinosyn A and D in paddy soil,water and other rice samples at 0.005-6.0 mg/kg spiked level were 72.9%-107.9% with relative standard deviations(RSD) of 1.1%-13.5%.The decline study of spinosad residue in paddy soil,water and rice plants suggested that the decline curves accorded with the first-order kinetics equation,and the half-lives of spinosad were 7.5,1.2,4.8 d,respectively.Spinosad belongs to the easily degradable pesticides.